Effect of Tartaric Acid on Activity and Thermosensitivity of Polyphenol Oxidase from the Edible Mushroom Agaricus bisporus

The effect of tartaric acid treatment at various concentrations on relative activity, thermostability and thermosensitivity of polyphenol oxidase(PPO) from the edible mushroom Agaricus bisporus was studied. The results showed that the relative activity of PPO decreased gradually with increasing tartaric acid concentration and was only 1.41% of its original activity when the tartaric acid concentration was up to 40 mmol/L. In addition, the thermostability of PPO decreased, and the inactivat ing effect of tartar ic acid combined with heat was enhanced. Inactivation rate constant(k) of PPO increased with increasing tartaric acid concentration, and the k values were 1.43 × 10-2, 2.43 × 10-2, 6.78 × 10-2, 57.61 × 10-2 min-1, respectively when the tartaric acid concentrations were 0, 10, 15 and 20 mmol/L at 50 ℃, while the activation energy(Ea) showed the opposite trend, which was calculated to be 191.57, 180.05, 140.64 and 67.93 kJ/mol, respectively, when the tartaric acid con centrations were 0, 10, 15 and 20 mmol/L, suggesting weakened thermosensitivity of PPO.